An important component of the lung's response to lipopolysaccharide (LPS) involves initiation of coagulation by Tissue Factor (TF), which binds to Factor Vila. The TF-VIIa complex activates Factor X and generates thrombin and fibrin in the alveolar and interstitial compartments. These coagulation proteins have specific pro-inflammatory effects in vitro, but their role in lung injury is not well understood. Specific blockade of the TF-VIIa complex attenuates inflammatory cytokine production and prevents lung injury after LPS instillation. This attenuated cytokine response includes IL-6, a cytokine that correlates with persistence of lung injury. I hypothesize that initiation of coagulation by TF coordinates the pulmonary inflammatory response to epithelial instillation of LIPS through enhanced IL-6 effector functions. The specific objectives of this proposal are: 1. Determine the role of alveolar Macrophage TF expression in early macrophage activation and IL-6 release in the lung after LPS. 2. Determine how specific steps in extrinsic coagulation (TF-VIIa, Xa or thrombin) regulate IL-6 expression in the lung after LPS exposure. 3. Determine whether selective modification of coagulation-mediated IL-6 inflammatory function protects the lung from LPS-mediated injury. The hypothesis will be tested in rats after intra-tracheal LPS instillation with and without specific blockade of coagulation. I will determine the effects of TF-VIIa inhibition on alveolar macrophage activation and IL-6 release. Regulation of IL-6 gene and protein expression by specific coagulation proteins will be determined and localized to specific lung cell types relative to activation of the transcription factors NF-KB and NF-11-6, and of MAP kinases, all involved in elaboration of IL-6. I will measure the effect of attenuated IL-6 expression after LPS on the following responses: IL-6 signal transduction (STAT-3), expression of LPS binding protein (LBP), vascular endothelial growth factor (VEGF). These molecular responses will be correlated with changes in macrophage and endothelial cell activation and capillary leak in the lung. The goal of this proposal is to elucidate one mechanism by which blockade of coagulation after LPS protects against inflammatory lung injury, and to define a specific role for IL-6 in coordinating the inflammatory response to initiation of coagulation by TF in the lung after LPS. These new data will be important to devise novel therapeutic approaches to acute lung injury based on cross-talk between inflammation and coagulation.